Check it before every single splash, no exceptions. Six hours gone because somebody skipped a two minute job is the kind of thing that makes you want to scream. The umbilical is the one thing keeping the diver alive down there, so how does nobody look at it first. Do it out loud too, say it back to each other so there is a witness. Being polite about it is how people get lazy and then somebody gets hurt. Say it plain and make it stick.